Known spectrometers can be based on the Fraunhofer diffraction equation, which is valid at long optical distances. As a result, these spectrometers have size constraints that can render them unsuitable for use in a variety of small-scale applications and devices. Some spectrometers have been based on Fresnel diffraction, which is valid at much shorter distances relative to Fraunhofer diffraction. However, known spectrometers employing Fresnel diffraction can suffer from various drawbacks.